I have heard that at 30' your scent will stay over their heads. I would think there would be several factors. Wind speed, direction and consistency. The terrain. Temperature. Time of day.Rising or falling temperature. Thermals.

Speed and direction, obviously. Wind flows over terrain differently. Say you are on the side of a steep hill with the wind blowing from behind you. In some cases, the wind will come over you and "eddy" back up to you. That swirl I would think would force your scent to the ground. If it is cold out, and the winds are calm, I would think the air coming from body being warmer would tend to rise, raising your scent with it.

Unfortunatley, this is all theory, but hey......it sounds good to me. [8D]

(I Really have read about the 30' thing though)